pH Indicators
7 test tubes
Added 5mL of water of 0.1 HCl and 5mL of water to 1st test tube.
Poured 9mL of water to remaining 6 test tubes.
Poured 1mL of solution from 1st test tube to 2nd.
Poured 1mL from 2nd to third.
Poured 1mL from 3rd to 4th.
" " 4th to 5th.
" " 5th to 6th.
" " 6th to 7th.
I added 2 drops of bromothymol blue to each and recorded color.
What is the Concentration(M) and the pH of each test tube?
How do I start?
YOu are diluting by a factor of 10 each time.
First tube (half water, half .1M)=.05M
Second tube=.005M
third tub=.0005M
Now check the first tube concentration, as I am not certain I intrepreted your Added right. It read as if it was half and half mixture.
Sorry, I meant 5mL of 0.1M HCl and 5mL of water.
To determine the concentration (M) and pH of each test tube, we need to understand the process and principles behind pH indicators. pH indicators are substances that can be added to a solution to determine its pH value based on a change in color.
In this experiment, you have started with 7 test tubes. The first test tube is a control, where you added 5 mL of water and 5 mL of 0.1 M HCl (hydrochloric acid) solution. The remaining 6 test tubes were filled with 9 mL of water each.
You then proceeded to create a series of dilutions by transferring small volumes from one test tube to the next. Starting from the first test tube, you took 1 mL and added it to the second test tube. Then, repeated this process by transferring 1 mL from the previous test tube to the next until you reached the seventh test tube.
After dilution, you added 2 drops of bromothymol blue indicator to each test tube and recorded the color change.
To determine the concentration (M) and pH of each test tube, you need to measure the change in color caused by the bromothymol blue indicator. The bromothymol blue indicator changes color depending on the acidity or alkalinity of the solution. Typically, it changes from yellow in acidic solutions to blue in alkaline solutions.
To start, compare the color of each test tube with the color chart provided for bromothymol blue indicator. Note down the observed color and refer to the chart to determine the approximate pH range associated with that color change.
Since you know the initial concentration for the first test tube (0.1 M HCl), you can use dilution calculations to determine the concentration in each subsequent test tube. The dilution factor for each transfer is 1:10, as you added 1 mL of solution to 9 mL of water each time. Multiply the initial concentration by the dilution factor to calculate the concentration of each test tube.
For example, if the initial concentration of HCl in the first test tube is 0.1 M, then the concentration in the second test tube would be 0.01 M (0.1 M × 1:10 dilution factor).
Repeat this calculation for each test tube to find the concentration (M) and then determine the approximate pH range associated with the observed color change using the color chart.